Larvae on Blackberries

I have blackberries with small white-ish-brown larvae, about 3mm, on/in them. Does anyone know what they are? If so, any way to tell what berries are infected without taking the berry apart? Anything I can do about it to treat/prevent? Should I cut the canes now? Cheers!

They probably would get inside. Some of my blueberries have tiny caterpillars coming out of them, I just discard any that have holes in them, a gentle squeeze of the damaged ones makes them shoot out of the tiny hole that has been made.

I bought a blueberry Top Hat from a reputable supplier who informed me that I would only need the one plant of this variety to fruit. It arrived with a few small berries but most dropped off, so I have pruned it right back. Hopefully I will get fruit next year? I have repotted using ericaceous compost.

I'm not familiar with the Top Hat variety, I've just had a look at a picture of one and it certainly looks impressive for the small size it will grow to, it looks like it will give as much fruit as the taller varieties.

I've found a page for blueberry care which gives full instructions. We have two plants and the first year we had very few berries, they are now in their third fruiting year and this year we have had loads off of them, the only pruning I have done so far is to cut out any dead bits and cut back any stems that have broken when they've got caught in the sliding doors on the greenhouse. It seems that they fruit on wood that is between one and three years old so I will have to thin out some growth when the time is right (February/March time).